The problem with assumptions: Revisiting "The dark figure of sexual recidivism"

What is the actual rate of sexual recidivism given the well-known fact that many crimes go unreported? This is a difficult and important problem, and in "The dark figure of sexual recidivism," Nicholas Scurich and Richard S. John (2019) attempt to make progress on it by "estimat[ing] actual recidivism rates . . . given observed rates of reoffending" (p. 171). In this article, we show that the math in their probabilistic model is flawed, but more importantly, we demonstrate that their conclusions follow ineluctably from their empirical assumptions and the unrepresentative empirical research they cite to benchmark their calculations. Scurich and John contend that their analysis undermines what they call the "orthodoxy in academic circles" (p. 173) of low sexual recidivism rates among individuals convicted of sexual offenses, but we underscore that their article does not analyze data in the traditional sense; instead, it just interprets past scholarly work through the use of strong assumptions in a way that, for practitioners, is likely to be opaque and misleading (and, for us, strays into speculation, argument, or advocacy and away from objective research). Our simple calculations show that their findings are highly sensitive to their assumptions, and we conclude that courts and others should recognize Scurich and John's work for what it is-a set of complex hypotheticals that are no more reliable than what judges and lawyers accomplish on their own by simply recognizing the basic problem that not all sexual offenses are reported.